Can You Be Allergic to Cats but Not Dogs? Decoding Pet Dander

When to Seek Urgent Help

Pet allergies usually cause uncomfortable but manageable symptoms. However, in rare cases, animal exposure can trigger a severe allergic reaction. Know when to act immediately.

The Science in Plain English

Why Cat and Dog Allergens Are Different

The reason you can be allergic to one species but not the other comes down to biology. "Pet dander" is often used as a catch-all term, but the allergenic proteins produced by cats and dogs are quite different:

• Cat allergen (Fel d 1): The major cat allergen is a protein called Fel d 1, produced primarily in the sebaceous glands, saliva, and skin of cats. It is extremely lightweight and sticky — it clings to clothing, furniture, and soft furnishings, and can remain airborne for hours. This is why cat allergen is found even in homes and buildings where no cat lives.
• Dog allergen (Can f 1): The primary dog allergen, Can f 1, is found in saliva, dander, and urine. While it also becomes airborne, it tends to settle more quickly than Fel d 1 and is generally present in lower concentrations in indoor environments.

Because these are structurally distinct proteins, your immune system treats them independently. You can produce IgE antibodies against Fel d 1 (cat) without producing them against Can f 1 (dog), or the other way around. Some people are sensitised to both; others to neither.

What Is IgE-Mediated Allergy?

Animal allergies — like most classical allergies — are driven by immunoglobulin E (IgE). When a sensitised person inhales, touches, or is otherwise exposed to a pet allergen, their IgE antibodies trigger mast cells to release histamine and other chemicals. This produces the familiar symptoms: sneezing, itchy eyes, nasal congestion, skin rashes, or in more serious cases, wheezing and breathing difficulty.

This is a different mechanism from food intolerance, which does not involve IgE. For more on this distinction, our guide on dairy allergy vs lactose intolerance explains the difference in practical terms.

Sensitisation vs Clinical Allergy

This is a crucial distinction that many online resources overlook:

• Sensitisation means your blood contains IgE antibodies against a specific allergen (e.g., cat dander). A pet dander test can detect this.
• Clinical allergy means you actually experience symptoms when exposed.

Some people test positive for cat or dog sensitisation but live happily with pets and never develop symptoms. Others may have symptoms despite borderline test results. This is why allergy test results must always be interpreted alongside your real-world experience — they support clinical assessment, they do not replace it.

Common Symptoms: Cat Allergy vs Dog Allergy

The symptoms of cat and dog allergy overlap considerably, which is why testing — rather than guessing — is important for identifying your specific triggers.

A notable difference: cat allergy symptoms often appear even without a cat being present in the room. Fel d 1 is so persistent and lightweight that it is commonly found on public transport seats, in offices, and in classrooms — carried in on clothing. Dog allergen, while still an indoor allergen, does not travel as readily.

How Pet Dander Testing Works

IgE Blood Testing for Animal Allergens

An IgE blood test is the most practical way to identify whether you are sensitised to cat, dog, or other animal allergens. Here is how it works:

• A venous blood sample is collected by a trained nurse or phlebotomist — a straightforward procedure taking around 15–20 minutes.
• The sample is sent to an accredited laboratory, where it is tested for allergen-specific IgE antibodies against individual animal proteins (e.g., Fel d 1 for cat, Can f 1 for dog).
• Results are returned as numerical values (kU/L), indicating the degree of sensitisation to each allergen tested.

Blood testing has several practical advantages for pet allergy investigation:

• No need to stop antihistamines — many pet allergy sufferers take daily antihistamines, and blood tests are unaffected by them.
• Unaffected by skin conditions — if you have eczema or dermatitis (which is common alongside animal allergy), blood testing avoids the complications of skin prick testing on inflamed skin.
• Tests multiple allergens from one sample — a single blood draw can screen for cat, dog, and other indoor allergens simultaneously.
• Zero risk of allergic reaction — the allergen is never introduced to your body.

For a broader comparison of blood testing versus other methods, see our article on blood test vs skin prick: which allergy test is more accurate.

What About "Hypoallergenic" Breeds?

A common question — and a common misconception. No cat or dog breed is truly hypoallergenic. All cats produce Fel d 1 and all dogs produce Can f 1, regardless of breed, coat length, or shedding pattern. Some breeds may produce lower levels of certain allergens, but there is no guarantee that a specific breed will not trigger symptoms in a sensitised individual.

Rather than choosing a pet based on marketing claims, a pet dander test can give you objective data about which species you are sensitised to — a much more useful starting point for decision-making.

What Results Can (and Can't) Tell You

Interpreting Positives and Negatives

• A positive result (elevated specific IgE to cat or dog) confirms sensitisation — your immune system recognises that allergen. It does not automatically mean you will have symptoms every time you encounter the animal.
• A negative result makes IgE-mediated allergy to that animal less likely, but does not completely rule it out. If your symptoms strongly correlate with pet exposure, discuss the result with your clinician.

Cross-Reactivity Between Animals

Some animal allergens share structural similarities with others. For example:

• Cat and other felines: Sensitisation to Fel d 1 can sometimes produce cross-reactive results to other cats (e.g., big cats in zoo environments), though this is rarely of practical concern.
• Dog and other mammals: Serum albumin proteins are shared across many mammalian species. A person sensitised to dog serum albumin may also show positive results to cat, horse, or rodent albumin — even if their main symptoms are only with dogs.
• Pork-cat syndrome: A lesser-known cross-reactivity where sensitisation to cat serum albumin (Fel d 2) can be associated with reactions to undercooked pork in some individuals.

These patterns are one reason why interpreting allergy results requires clinical context — a positive test alone is not a diagnosis.

Why a Number Cannot Predict Severity

A higher specific IgE level does not necessarily mean a more severe reaction. Some people with very high cat IgE live with cats and manage mild symptoms; others with lower levels experience significant breathing problems. Reaction severity depends on allergen dose, individual sensitivity, co-factors (such as concurrent illness or exercise), and whether asthma is present.

Living with Pets When You Have an Animal Allergy

Many competitor resources jump straight to "rehome your pet" as the primary recommendation. While avoidance is the most effective way to reduce allergen exposure, we recognise that pets are family members — and rehoming is not always realistic or desirable.

If you have confirmed sensitisation to a pet you live with, here are evidence-based strategies to help manage a pet-friendly home alongside your allergy:

Reducing Indoor Allergen Levels

• Create pet-free zones — keeping the bedroom pet-free can significantly reduce overnight allergen exposure, which is when many people notice the worst symptoms.
• Use HEPA air purifiers — high-efficiency particulate air (HEPA) filters can reduce airborne pet dander, particularly in rooms where pets spend time.
• Wash bedding and soft furnishings regularly — pet allergens cling to fabrics. Washing at 60°C can help reduce allergen levels.
• Vacuum with a HEPA-filter vacuum — standard vacuums can redistribute fine allergen particles into the air. A HEPA-filter model traps them.
• Wipe down hard surfaces — damp-dusting and mopping removes settled allergen more effectively than dry dusting.
• Wash hands after handling pets — this reduces transfer of allergen to the eyes, nose, and mouth.

When to Consider Further Clinical Support

If your symptoms remain poorly controlled despite environmental measures and over-the-counter antihistamines, it is worth discussing your situation with a GP or allergy specialist. Options they may consider include:

• Prescription-strength nasal sprays or eye drops
• A review of whether asthma is being adequately managed
• Referral for specialist assessment if symptoms are severe or affecting quality of life

Having objective test data — showing exactly which allergens you are sensitised to — makes these conversations more productive and can help your clinician tailor advice to your specific situation.

Practical Next Steps (UK Pathway)

1. Keep a Symptom and Exposure Diary

Before booking a test, start recording when symptoms occur, where you were, and which animals you were in contact with. Note whether symptoms happen at home, at friends' houses, at work, or in other environments. This pattern-spotting is invaluable for your clinician and can help determine which allergens to test for.

2. Get Tested to Identify Your Specific Triggers

Rather than guessing, an IgE blood test can objectively measure your sensitisation to individual animal allergens. You can continue taking antihistamines in the lead-up to the test, and results are returned within several working days. Explore the allergy blood test panels available to find the right option for your symptoms.

3. Use Data to Make Informed Decisions

With clear results, you can make practical decisions: Is it the cat, the dog, or both? Should you focus on environmental controls? Is the issue pet-related at all, or could another indoor allergen — such as dust mites — be the real culprit? Testing removes the guesswork.

4. Plan Exposure Management Strategies

Armed with your results, you can implement targeted allergen reduction measures for the specific animal(s) you are sensitised to — rather than applying generic advice that may not address your actual triggers. If seasonal factors such as hay fever are also involved, managing both together can make a real difference to your quality of life.

Frequently Asked Questions

Summary

Cat and dog allergens are biologically distinct proteins, which is why you can absolutely be allergic to one species but not the other. Guessing which animal is the problem — or assuming you need to rehome a pet — is not necessary when objective testing is available.

• Cat allergy is driven primarily by Fel d 1; dog allergy by Can f 1 — your immune system treats them independently.
• An IgE blood test can identify exactly which animal allergens you are sensitised to, from a single blood sample.
• Blood testing works regardless of antihistamine use, skin conditions, or age.
• Results give you objective data to manage pet ownership, implement targeted allergen reduction, and have informed discussions with your clinician.
• Sensitisation does not always equal clinical allergy — results should be interpreted alongside your symptoms.

If you would like to find out which animals you are sensitised to, our nurse-led venous blood testing offers clear, laboratory-verified results — no need to stop your antihistamines, and suitable for all ages. Browse our allergy blood test panels to see what\u2019s available, or get in touch if you have questions about the booking process.

References Used

• NHS — Allergies — Overview
• Allergy UK — Pet Allergy
• BSACI — Guidelines for the Management of Allergy
• Anaphylaxis UK — Understanding Anaphylaxis
• Bonnet B et al. "An update on molecular cat allergens: Fel d 1 and what else?" Allergy, Asthma & Clinical Immunology, 2018; 14:14.
• Konradsen JR et al. "Allergy to furry animals: New insights, diagnostic approaches, and challenges." Journal of Allergy and Clinical Immunology, 2015; 135(3):616–625.
• Liccardi G et al. "Focus on cat allergen (Fel d 1): immunological and aerodynamic characteristics, modality of airway sensitisation and avoidance strategies." International Archives of Allergy and Immunology, 2003; 132(1):1–12.